/Engine/Source/Runtime/Engine/Public/SaveGameSystem.h
Asyncronously checks if the named savegame exists. Default implementation runs blocking version on a background thread
virtual void DoesSaveGameExistAsync ( const TCHAR * Name, [FPlatformUserId](API\Runtime\Core\Misc\FPlatformUserId) PlatformUserId, [FSaveGameAsyncExistsCallback](API\Runtime\Engine\ISaveGameSystem\FSaveGameAsyncExistsCallback) Callback )